As can be seen by reference to the following U.S. Pat. Nos. 4,903,245; 4,751,418; 2,396,935; and 4,649,524; the prior art is replete with myriad and diverse acoustical monitoring systems and electroacoustic transducers.
While all of the aforementioned prior art constructions are more than adequate for the basic purpose and function for which they have been specifically designed, these patented systems have never before been employed in the specific environment or in the same way as proposed in the present invention.
In the past attempts had been made to acoustically monitor mining equipment with microphones to ascertain by the deviations in noise levels when the cutting head of a miner was encountering rock or coal. Unfortunately the ambient sounds of the conveyor, hydraulic pump, ventilation system and other noise sources masked the cutting sounds and did not produce reliable results that could be depended upon by the machine operator situated at a remote location.
In one instance a longwall shearer was equipped with a sensitized pick which responded to instantaneous changes in cutting force. However a computer was coupled to the output of the pick and was unable to detect successfully contact between the shearer and the rock roof above the seam of coal.
As a consequence of the foregoing situation, there has existed a longstanding need in the mining industry to provide the machine operator with cutter head vibration information on a real time basis via an audio system; and, the provision of such a construction is a stated objective of the present invention.